Piston



atented Jan. i3, 1925.

GEORGE CALVIN AUsTiN, or

TACO, WASHINGTON, ASSIGNOR T0 RAY E. DAY, 0F

TCOMA, WASHINGTON.

PISTON.

Application led May 17, 1921, Serial No. 470,382. Renewed July 18, 1923.

To all whom it may concern:

Bc it known that I, GEORGE CALVIN AUS- TIN, a citizen of the United States, and a resident of the city of Tacoma, county of Pierce, State of Washington, have invented certain new and useful Improvements in Pistons, of which the following is a speciication.

My invention relates to improvements in pistons and the principal' object of my invention is to provide a piston made of metal having a comparatively high coefficient of expansion, such as aluminum alloy, and which is so constructed that the. diametrical expansion of the piston incidental to heating in operation is controlled` thereby making it possible to minimize the diametrical expansion of the piston and making it practicable to fit the piston to an engine cylinder with less clearance than would otherwise be possible.

To obtain this, a construction is illustrated in the accompanying drawings which show two pairs of segmented bands cast within the piston walls, the latter being so slotted as to permit expansion thereof to take place circumferentially, by slipping on said bands.

A further object of the. invention is to lprovide a piston of the above character wherein the ends of each segmented pair of bands are made to overlap each other, so that in heating, the diameter of the piston will be reduced because of the difference of coefficients of expansion of the metals employed. Varying amounts of overlap may be used, thereby making it practicable to design the piston so that in heating, lthe diameter will not become greater than the normal expansion of the bands; or that, in heating, the diameter of the piston will remain constant; or that, in heating, the diameter of the piston will reduce to any desirable lpredetermined degree within the limits of the coefiicients of expansion of the metals employed in the construction of the piston.

ln accomplishing these and other objects of the invention, Ijhave provided the improved details of construction, the preferred forms of which are illustrated in the accompanying drawings, wherein-- Figure 1 is a side elevation of a piston constructed'according to the present invention, partly broken away for better illustration.

Figure 2 is a transverse sectional view ot' the same taken on the line 2-2 in Figure l. y

Figure 3 is a section taken on the line 3 3 in Figure 2.

li`igure4 is a section on the line 4-4 in Figure 2.

Figure 5 is a view of one of the bands used in the piston. f

Referring more in detail to the several vviews of the drawings, wherein like reference numerals designate the same or like partsl designates as a whole, a piston constructed according to the present invention, and which is of'. the usual piston form, open at its lower end for the reception of a connecting rod and closed at its upper' end by a head 2 which is reinforced by an underlying, transverse web 3 cast integrally with the head and side walls and extended diametrically across the piston. l/Vrist pin bosses 4 and 5 are cast integral with the walls about midway of the length of the piston, for the reception of a wrist `pin to which a connecting rod may be attachedg these two latter parts notbeing shown in the present drawing.

The skirt of the piston is provided at opposite sides, with longitudinally c irected slots 7, which extend from the open end to near the closed upper end of the piston and which, at their upper ends open into slots 8 which are directed circumferentially about the piston in a plane that is parallel with the plane of the end wall 2. These latter slotspterminate above, and at opposite sides of the wrist pin bosses and at opposite sides of the web 3, so that the skirt is joined to the upper end of the piston by the web portion and by sol-id necks of metal directly above the bearing bosses.

To give the necessary strength and rigidity to the piston skirt and to control diametricul expansion of the piston. I have cast annular ianges l0 and 11 within the same, which are located respectively near the upper and lower ends of the slots 7, and have cast within these flanges paired segmental, expansion controlling bauds l2 which preferably would be of steel, or Iother suitable metal whose coelicientof expansion is relatively small as compared with that of the body forming metal. These bands are disposed in pairs in oppositerelation, as shown best in Figure 1, whereinl the ends of paired result the rings are provided at their ends' with heads 15, and are then given a coatin of (graphite paste or otherl suitable materia an are placed in the casting mold in such position that when thepiston isformed the ends of the bands/will be overlapped across the plane of the wrist pin bosses and the notches `in the bandswill'receive the metal of the piston walls therein so that they are securely anchored against slippage at these points. Slippage at all other points is provided for, however, due to the coating of graphite which holds the metal, when cast, away from the bands, and when the metal: contracts in cooling, it permits the necessary contraction due to its compressibility, without allowing adhesion tothe bands.

Another result obtained from the use of the graphite paste is its action as a lubricant for facilitating slippage of the walls on the bands when the piston expands or contracts.

In the making of such a piston, the upper, closed end would be equipped with theusual (piston rings 20, and this end would be made slightly smaller in diameter than the'skirt portion to make allowance for -a greater ex- Y chored within the walls between the slots.

pansion of this end of the piston.

With a piston so constructed, it isy apparent that circumferential expansion of the skirt walls may be taken up 'iii the lon 'tudinal slots 7, and warping, that Woul possibly occur by a greater expansion of the head'end than the skirt, is eliminated by the provision of the slots 8. l A

` It is also apparent that the bands 12 will strengthen the skirt, and will not, on account of the way they are slidably contained, cause any damage or cracking of the walls by eX- pansion or contraction.

It is also, to be noted that Ithe anchoring of the expansion controlling bands at opposite sides of the pistons prevents the side pressure Aof t-he piston against the cylinder *Walls from compressing the piston aty one side and expanding it at the other side as would occur without such anchoring.

It will be observed that when a piston of this construction is'heated in operation that the diameter of the piston will be substantially no greater than permitted by the normal expansion of the bands minus the difference in the coeicients of expansion of within said walls and across said slots and anhored within said walls at their 'opposite en s. v Y

2. A piston of the character described, made of metal having a'relatively high coeiicient of expansion, and having longitudinal. expansion slots at' opposite sides thereof, segmental bands, or strips, of metal, having a relatively low coeilicient o-expansion, disposed within opposite sides of said pistoni with their ends overlappedr and anchored within said piston walls between said slots said bands being slidable within the walls except at the anchored ends and extended across said'fslots and adapted to pre# vent diametrical expansion of the piston beyond that permitted by the normal expansion ofthe bands.

3. A piston of the character described,

made of metal having a relatively high coefficient of expansion, and having longitudinal expansionslots at opposite sides thereof, segmental bands, or strips, of metal, having a relatively low coeicient of e ansion, disposed within opposite sides of sdi piston with their ends overlapped andhaving heads formed at their ends whereby they are ancompared to that of the piston, withinthe piston walls at opposite sides thereof with their ends overlapped, and secured at their ends only to said walls and 'varying the -extent of overlap as required to ,retain the ics diameter of the piston substantially conl stant regardless of above normal. ,f v

5. A piston of the character described, made of a metal having a relatively high coefficient `oiexpansion and having an expan` any rise in temperature sion slot in the walll thereof, and a split band of metal having a relatively low co,- eficient oi expansion slidably disposed within said wall and extendingacross-said slot( and being anchored at its ends in said r,

wall.

6. 'A piston of the character described, made of a metal having a relatively high coeicient of expansion and having an expansion slot in its skirt, and a segmental band embedded in and extending circumferentially of said skirt, said segmental band having its ends anchored in said skirt against move- A ment, the remainder of said band being unattached to said skirt and extending across said expansion slot and adapted to lievent diametrical expansion of the piston yond that permitted bythe normal expansion of 10 the band. Signed day of M 

